It is known that, in such a stabilized low speed flight phase, the lift provided for the aircraft by its wings and by the said movable aerodynamic surfaces must be high, such that this high lift (possibly strengthened by the blowing over the wings by the propellers of the engines and possibly aided by the traction force of the latter) generates a high diving moment with respect to the center of gravity of the aircraft.
In order to trim the aircraft, the pilot deflects the elevators of the said aircraft to pitch-up, in such a way that the latter generate, with respect to the said center of gravity of the aircraft, a pitch-up moment capable of counteracting the said high diving moment.
However, if during such a stabilized low speed flight phase the aircraft has to suddenly avoid another aircraft by flying under it in order to avoid a collision, the pilot suddenly sets the elevators to full dive. Then, after the avoidance, the elevators are again returned, from their full dive position, to a pitch-up position allowing the aircraft to carry out a pull-out.
It will easily be understood that the success of such a maneuver requires a large sizing of the said elevators and of their actuating means, which are generally hydraulic.